Thrombectomy
Mechanical thrombectomy, or simply thrombectomy, is the removal of a blood clot from a blood vessel, often and especially endovascularly as an interventional radiology procedure called endovascular thrombectomy. It thus contrasts with thrombolysis by thrombolytic medications, as either alternative or complement thereto. It is commonly performed in the cerebral arteries as treatment to reverse the ischemia in some ischemic strokes. Open vascular surgery versions of thrombectomy also exist. The effectiveness of thrombectomy for strokes was confirmed in several randomised clinical trials conducted at various medical centers throughout the United States, as reported in a seminal multistudy report in 2015.
Applications in brain
Ischemic stroke represents the fifth most common cause of death in the western world and the number one cause of long-term disability. Until recent times, systemic intravenous fibrinolysis was the only evidence-based therapy for patients with acute onset of stroke due to large vessel occlusion.History
The world's first thrombectomy was performed in 1994 at Sahlgrenska University Hospital, Gothenburg, Sweden by senior physician Gunnar Wikholm.In 2015, the results of five trials from different countries were published in the New England Journal of Medicine, demonstrating the safety and efficacy of mechanical thrombectomy with stent-retrievers in improving outcomes and reducing mortality for patients who present within six hours from their time last known well. It is now a widespread procedure performed in many hospitals around the globe, especially comprehensive stroke centers, although many other hospitals are not yet able to supply the service enough to meet the need. Large obstacles to making EVT more widely available are both systematic hurdles at the prehospital stages and the intrahospital barrier of a scarcity of interventional neuroradiologists. They concern TTR, which is the same underlying problem as the golden hour in general, albeit several hours in the case of TTR: that is, EVT performed within 2 or 3 hours can help vastly, whereas EVT performed after 6 to 12 hours is often too late to prevent the permanent sequelae of the ischemia. In this respect, the dissemination of EVT into clinical practice shows how translational medicine has various layers, some easier to solve and some harder: it was in some respects straightforward to develop the technology of EVT in the 2000s and 2010s, but it is not easy to revamp the standard of care in prehospital settings, which deployment of timely EVT requires.
In 2018 the DAWN and DEFUSE-3 trials were published. These trials showed that mechanical thrombectomy is a safe and effective treatment for individuals who have an acute ischemic stroke, even out to 24 hours after symptom onset. Most studies, however, have focused on thrombectomies in anterior circulation strokes. In recent years, increasing evidence on the efficacy of mechanical thrombectomy in posterior circulation strokes has been published.
Stent-retriever thrombectomy
The procedure can be performed with general anesthesia or under conscious sedation in an angiographic room. A system of coaxial catheters is pushed inside the arterial circulation, usually through a percutaneous access to the right femoral artery. A microcatheter is finally positioned beyond the occluded segment and a stent-retriever is deployed to catch the thrombus; finally, the stent is pulled out from the artery, usually under continuous aspiration in the larger catheters.Direct aspiration
A different technique for mechanical thrombectomy in the brain is direct aspiration. It is performed by pushing a large soft aspiration catheter into the occluded vessel and applying direct aspiration to retrieve the thrombus; it can be combined with the stent-retriever technique to achieve higher recanalization rates, but the complexity of the procedure increases.Direct aspiration has not been studied as thoroughly as stent-retriever thrombectomy, but it is still widely performed because of its relative simplicity and low cost.